Since fat graft was first introduced in 1893 by Neuber, various methods have been suggested [10
]. Adipose tissue is easily and repeatedly obtained, and fat graft is a simple and low-risk procedure. Accordingly, fat graft is now one of the most common and widely used procedures in plastic surgery. Because the fat tissue used in these procedures is autologous, no side effects caused by immune responses have been reported, and any part of the body can be a recipient site. However, grafted fat can be absorbed into the body, and the level of absorption is difficult to anticipate. In addition, results can be significantly different from surgeon to surgeon and accordingly, quantitative analysis and evaluation of fat grafts are not easy.
Studies on embryonic stem cells and adult stem cells are active in the field of biotechnology [5
]. Embryonic stem cells are ideal stem cells for tissue reconstruction because they can differentiate into various tissues. However, differentiation of embryonic stem cells is difficult to control, and the risk of malignant degeneration is present. Ethical issues are another factor restricting their clinical applications [6
]. In contrast, adult stem cells are obtained from already differentiated tissues, and are free from ethical controversy. Among adult stem cells, adipose stem cells are actively studied because they are easily obtainable. According to an in vitro experiment conducted by Zuk et al. [3
], adipose stem cells can differentiate into cells of fat, cartilage, muscle, and bone. In practice, the clinical application of adipose stem cells in a graft is not easy because cell culture facilities that gain the approval of the Korea Food and Drug Administration need to be used. Due to these limitations, recent studies have focused on SVF cells that are obtained when adipose tissue is centrifuged without the use of cultivation. Leblanc et al. [11
] reported that SVF cells obtained from adipose tissue increased blood flow in the coronary artery after the development of myocardial infarction. Lendeckel et al. [12
] reported cases of successful bone reconstruction using fibrin glue and SVF cells obtained from adipose tissue, which were grafted into the area of the cranial defect.
In the present study, we tried to delay or prevent absorption of fat after grafting by mixing SVF cells with adipose tissue. At postoperative 12 weeks, the patient and doctor surveys confirmed that the results of grafts with adipose tissue mixed with SVF cells were better than those grafted with adipose tissue without SVF cells in all 5 categories of volume consistency, softness, irregularity, naturality, and overall satisfaction. As suggested by multiple studies [11
], SVF cells have been considered to facilitate the growth of surrounding tissues. In the present study, this function of SVF cells was observed. However, the mechanism of SVF cells facilitating the growth of surrounding fat cells is not clearly understood. Additional studies investigating this issue are expected in the future.
According to the present study, the highest evaluation score after a fat graft mixed with SVF cells was assigned to the nasolabial fold followed by the malar eminence and infraorbital region (, ). In our previous study [2
], the lowest satisfaction score after graft was assigned to the nasolabial fold area. The reason for the different results between the previous and the present study is considered to be due to the SVF cells used in the present study having a remarkable effect in the area of nasolabial fold, which usually has low satisfaction scores due to the deepness of the fold.
Quantitative analysis or measurement of the adipose tissue that remains after a fat graft is difficult to perform in practice. Therefore, the effects of the fat grafts were evaluated through surveys using the clinical photos. However, this method is limited by the subjective nature of the evaluation carried out by the patients or surgeons. In the future, an objective and quantitative method of measuring the fat amount should be developed to calculate the survival rate of SVF cells that are mixed with adipose tissue.
In order to establish a control group, the right side of the face of the patients was grafted with adipose tissue without SVF cells. Consequently, bias was minimized in the present study. Even though this method was used with the permission of the patients, there was a risk of causing an imbalance in the appearance of the right and left side of the face in the patients. For this reason, only 9 patients were enrolled in the present study. A larger number of patients, and a more accurately established control group than the present study may be necessary to obtain more reliable data on the effects of SVF cells on the survival rate of fat cells.
Moreover, there were some limitations to the present study. First, facial bone computed tomography was conducted only at 12 weeks postoperatively. However, it was not conducted immediately after the fat grafts were performed. If we conduct facial bone computed tomography immediately after the operation and at 12 weeks postoperatively, it may measure the absorption rate of fat cells. Second, only 9 patients were enrolled in this study and the follow-up period for the evaluation results was 12 weeks postoperatively. If the number of patients and the follow-up period were increased, it could verify the effects of SVF cells on the survival rate of fat cells.
The positive effects of SVF cells on the generation and long-term survival rate of adipose tissue were confirmed in the present study. In particular, the effects of SVF cells were more evident in the area of deep wrinkles in the face than in other areas. In conclusion, fat grafts using SVF cells may enhance the survival rate of fat cells and the effects of fat grafts.